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Wasm: add support for overflow checks on signed and unsigned ints multiply #8259

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merged 7 commits into from
Aug 26, 2020
Merged

Wasm: add support for overflow checks on signed and unsigned ints multiply #8259

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a1ce3e8
wasm-ovf-unsigned-int
yowl Aug 8, 2020
fe3dc9b
Merge remote-tracking branch 'origin/master' into wasm-mul-ovf-int
yowl Aug 11, 2020
3bd7933
refactor for stack kind tests and add signed check
yowl Aug 12, 2020
e9f31f7
Merge remote-tracking branch 'origin/master' into wasm-mul-ovf-int
yowl Aug 26, 2020
060915f
use llvm intrinsics
yowl Aug 26, 2020
c661dda
remove unused function/fields
yowl Aug 26, 2020
eb5549d
Merge remote-tracking branch 'origin/master' into wasm-mul-ovf-int
yowl Aug 26, 2020
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127 changes: 109 additions & 18 deletions src/ILCompiler.WebAssembly/src/CodeGen/ILToWebAssemblyImporter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2782,15 +2782,15 @@ private bool ImportIntrinsicCall(MethodDesc method, MethodDesc runtimeDetermined
// then
builder.PositionAtEnd(notFatBranch);
ExceptionRegion currentTryRegion = GetCurrentTryRegion();
LLVMValueRef notFatReturn = CallOrInvoke(fromLandingPad, builder, currentTryRegion, fn, llvmArgs, ref nextInstrBlock);
LLVMValueRef notFatReturn = CallOrInvoke(fromLandingPad, builder, currentTryRegion, fn, llvmArgs.ToArray(), ref nextInstrBlock);
builder.BuildBr(endifBlock);

// else
builder.PositionAtEnd(fatBranch);
var fnWithDict = builder.BuildCast(LLVMOpcode.LLVMBitCast, fn, LLVMTypeRef.CreatePointer(GetLLVMSignatureForMethod(runtimeDeterminedMethod.Signature, true), 0), "fnWithDict");
var dictDereffed = builder.BuildLoad(builder.BuildLoad( dict, "l1"), "l2");
llvmArgs.Insert(needsReturnSlot ? 2 : 1, dictDereffed);
LLVMValueRef fatReturn = CallOrInvoke(fromLandingPad, builder, currentTryRegion, fnWithDict, llvmArgs, ref nextInstrBlock);
LLVMValueRef fatReturn = CallOrInvoke(fromLandingPad, builder, currentTryRegion, fnWithDict, llvmArgs.ToArray(), ref nextInstrBlock);
builder.BuildBr(endifBlock);

// endif
Expand All @@ -2806,7 +2806,7 @@ private bool ImportIntrinsicCall(MethodDesc method, MethodDesc runtimeDetermined
}
else
{
llvmReturn = CallOrInvoke(fromLandingPad, builder, GetCurrentTryRegion(), fn, llvmArgs, ref nextInstrBlock);
llvmReturn = CallOrInvoke(fromLandingPad, builder, GetCurrentTryRegion(), fn, llvmArgs.ToArray(), ref nextInstrBlock);
}

if (!returnType.IsVoid)
Expand All @@ -2829,23 +2829,21 @@ private bool ImportIntrinsicCall(MethodDesc method, MethodDesc runtimeDetermined
}

LLVMValueRef CallOrInvoke(bool fromLandingPad, LLVMBuilderRef builder, ExceptionRegion currentTryRegion,
LLVMValueRef fn, List<LLVMValueRef> llvmArgs, ref LLVMBasicBlockRef nextInstrBlock)
LLVMValueRef fn, LLVMValueRef[] llvmArgs, ref LLVMBasicBlockRef nextInstrBlock)
{
LLVMValueRef retVal;
if (currentTryRegion == null || fromLandingPad) // not handling exceptions that occur in the LLVM landing pad determining the EH handler
{
retVal = builder.BuildCall(fn, llvmArgs.ToArray(), string.Empty);
retVal = builder.BuildCall(fn, llvmArgs, string.Empty);
}
else
{
nextInstrBlock = _currentFunclet.AppendBasicBlock(String.Format("Try{0:X}", _currentOffset));

retVal = builder.BuildInvoke(fn, llvmArgs.ToArray(),
retVal = builder.BuildInvoke(fn, llvmArgs,
nextInstrBlock, GetOrCreateLandingPad(currentTryRegion), string.Empty);

_curBasicBlock = nextInstrBlock;
_currentBasicBlock.LLVMBlocks.Add(_curBasicBlock);
_currentBasicBlock.LastInternalBlock = _curBasicBlock;
AddInternalBasicBlock(nextInstrBlock);
builder.PositionAtEnd(_curBasicBlock);
}
return retVal;
Expand Down Expand Up @@ -3902,10 +3900,26 @@ private void ImportBinaryOperation(ILOpcode opcode)

result = _builder.BuildSub(left, right, "sub");
break;
// TODO: Overflow checks
case ILOpcode.mul_ovf:
case ILOpcode.mul_ovf_un:
result = _builder.BuildMul(left, right, "mul");
Debug.Assert(CanPerformUnsignedOverflowOperations(op1.Kind));
if (Is32BitStackValue(op1.Kind))
{
result = BuildMulOverflowCheck(left, right, "umul", LLVMTypeRef.Int32);
}
else
{
result = BuildMulOverflowCheck(left, right, "umul", LLVMTypeRef.Int64);
}
break;
case ILOpcode.mul_ovf:
if (Is32BitStackValue(op1.Kind))
{
result = BuildMulOverflowCheck(left, right, "smul", LLVMTypeRef.Int32);
}
else
{
result = BuildMulOverflowCheck(left, right, "smul", LLVMTypeRef.Int64);
}
break;

default:
Expand All @@ -3922,6 +3936,32 @@ private void ImportBinaryOperation(ILOpcode opcode)
PushExpression(kind, "binop", result, type);
}

LLVMValueRef BuildMulOverflowCheck(LLVMValueRef left, LLVMValueRef right, string mulOp, LLVMTypeRef intType)
{
LLVMValueRef mulFunction = GetOrCreateLLVMFunction("llvm." + mulOp + ".with.overflow." + (intType == LLVMTypeRef.Int32 ? "i32" : "i64"), LLVMTypeRef.CreateFunction(
LLVMTypeRef.CreateStruct(new[] { intType, LLVMTypeRef.Int1}, false), new[] { intType, intType }));
LLVMValueRef mulRes = _builder.BuildCall(mulFunction, new[] {left, right});
var overflow = _builder.BuildExtractValue(mulRes, 1);
LLVMBasicBlockRef overflowBlock = _currentFunclet.AppendBasicBlock("ovf");
LLVMBasicBlockRef noOverflowBlock = _currentFunclet.AppendBasicBlock("no_ovf");
_builder.BuildCondBr(overflow, overflowBlock, noOverflowBlock);

_builder.PositionAtEnd(overflowBlock);
CallOrInvokeThrowException(_builder, "ThrowHelpers", "ThrowOverflowException");

_builder.PositionAtEnd(noOverflowBlock);
LLVMValueRef result = _builder.BuildExtractValue(mulRes, 0);
AddInternalBasicBlock(noOverflowBlock);
return result;
}

void AddInternalBasicBlock(LLVMBasicBlockRef basicBlock)
{
_curBasicBlock = basicBlock;
_currentBasicBlock.LLVMBlocks.Add(_curBasicBlock);
_currentBasicBlock.LastInternalBlock = _curBasicBlock;
}

bool CanPerformSignedOverflowOperations(StackValueKind kind)
{
return kind == StackValueKind.Int32 || kind == StackValueKind.Int64;
Expand Down Expand Up @@ -3995,7 +4035,7 @@ void BuildAddOverflowChecksForSize(ref LLVMValueRef llvmCheckFunction, LLVMValue
}

LLVMBasicBlockRef nextInstrBlock = default;
CallOrInvoke(false, _builder, GetCurrentTryRegion(), llvmCheckFunction, new List<LLVMValueRef> { GetShadowStack(), left, right }, ref nextInstrBlock);
CallOrInvoke(false, _builder, GetCurrentTryRegion(), llvmCheckFunction, new LLVMValueRef[] { GetShadowStack(), left, right }, ref nextInstrBlock);
}

void BuildSubOverflowChecksForSize(ref LLVMValueRef llvmCheckFunction, LLVMValueRef left, LLVMValueRef right, LLVMTypeRef sizeTypeRef, LLVMValueRef maxValue, LLVMValueRef minValue, bool signed)
Expand Down Expand Up @@ -4028,7 +4068,41 @@ void BuildSubOverflowChecksForSize(ref LLVMValueRef llvmCheckFunction, LLVMValue
}

LLVMBasicBlockRef nextInstrBlock = default;
CallOrInvoke(false, _builder, GetCurrentTryRegion(), llvmCheckFunction, new List<LLVMValueRef> { GetShadowStack(), left, right }, ref nextInstrBlock);
CallOrInvoke(false, _builder, GetCurrentTryRegion(), llvmCheckFunction, new LLVMValueRef[] { GetShadowStack(), left, right }, ref nextInstrBlock);
}

private LLVMValueRef CallLlvmAbs(LLVMBuilderRef builder, LLVMValueRef operand, LLVMTypeRef sizeTypeRef)
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Unused?

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yes, removed

{
// TODO: There is an LLVM intrinsic for this but couldn't make it work (llvm.abs.i32 or llvm.abs.i64)
bool is32 = sizeTypeRef.IntWidth == 32;
LLVMValueRef llvmAbsFunction = is32 ? Abs32Function : Abs64Function;
if (llvmAbsFunction.Handle == IntPtr.Zero)
{
llvmAbsFunction = Module.AddFunction("corert.abs" + sizeTypeRef.IntWidth,
LLVMTypeRef.CreateFunction(sizeTypeRef, new LLVMTypeRef[] { sizeTypeRef }, false));
LLVMValueRef opParam = llvmAbsFunction.GetParam(0);
LLVMBuilderRef absBuilder = Context.CreateBuilder();
var block = llvmAbsFunction.AppendBasicBlock("Block");
absBuilder.PositionAtEnd(block);
LLVMBasicBlockRef thenBlock = llvmAbsFunction.AppendBasicBlock("negBlock");
LLVMBasicBlockRef elseBlock = llvmAbsFunction.AppendBasicBlock("posBlock");
var ltZeroCmp = absBuilder.BuildICmp(LLVMIntPredicate.LLVMIntSLT, opParam, LLVMValueRef.CreateConstInt(sizeTypeRef, 0));
absBuilder.BuildCondBr(ltZeroCmp, thenBlock, elseBlock);
absBuilder.PositionAtEnd(thenBlock);
var negate = absBuilder.BuildNeg(opParam);
absBuilder.BuildRet(negate);
absBuilder.PositionAtEnd(elseBlock);
absBuilder.BuildRet(opParam);
if (is32)
{
Abs32Function = llvmAbsFunction;
}
else
{
Abs64Function = llvmAbsFunction;
}
}
return builder.BuildCall(llvmAbsFunction, new[] {operand}, "abs");
}

private void BuildOverflowCheck(LLVMBuilderRef builder, LLVMValueRef compOperand, LLVMIntPredicate predicate,
Expand Down Expand Up @@ -4534,7 +4608,7 @@ private void ThrowIfNull(LLVMValueRef entry)
}

LLVMBasicBlockRef nextInstrBlock = default;
CallOrInvoke(false, _builder, GetCurrentTryRegion(), NullRefFunction, new List<LLVMValueRef> { GetShadowStack(), entry }, ref nextInstrBlock);
CallOrInvoke(false, _builder, GetCurrentTryRegion(), NullRefFunction, new LLVMValueRef[] { GetShadowStack(), entry }, ref nextInstrBlock);
}

private void ThrowCkFinite(LLVMValueRef value, int size, ref LLVMValueRef llvmCheckFunction)
Expand Down Expand Up @@ -4577,16 +4651,33 @@ private void ThrowCkFinite(LLVMValueRef value, int size, ref LLVMValueRef llvmCh
}

LLVMBasicBlockRef nextInstrBlock = default;
CallOrInvoke(false, _builder, GetCurrentTryRegion(), llvmCheckFunction, new List<LLVMValueRef> { GetShadowStack(), value }, ref nextInstrBlock);
CallOrInvoke(false, _builder, GetCurrentTryRegion(), llvmCheckFunction, new LLVMValueRef[] { GetShadowStack(), value }, ref nextInstrBlock);
}

private void ThrowException(LLVMBuilderRef builder, string helperClass, string helperMethodName, LLVMValueRef throwingFunction)
{
LLVMValueRef fn = GetHelperLlvmMethod(helperClass, helperMethodName);
builder.BuildCall(fn, new LLVMValueRef[] {throwingFunction.GetParam(0) }, string.Empty);
builder.BuildUnreachable();
}

/// <summary>
/// Calls or invokes the call to throwing the exception so it can be caught in the caller
/// </summary>
private void CallOrInvokeThrowException(LLVMBuilderRef builder, string helperClass, string helperMethodName)
{
LLVMValueRef fn = GetHelperLlvmMethod(helperClass, helperMethodName);
LLVMBasicBlockRef nextInstrBlock = default;
CallOrInvoke(false, builder, GetCurrentTryRegion(), fn, new LLVMValueRef[] {GetShadowStack()}, ref nextInstrBlock);
builder.BuildUnreachable();
}

LLVMValueRef GetHelperLlvmMethod(string helperClass, string helperMethodName)
{
MetadataType helperType = _compilation.TypeSystemContext.SystemModule.GetKnownType("Internal.Runtime.CompilerHelpers", helperClass);
MethodDesc helperMethod = helperType.GetKnownMethod(helperMethodName, null);
LLVMValueRef fn = LLVMFunctionForMethod(helperMethod, helperMethod, null, false, null, null, out bool hasHiddenParam, out LLVMValueRef dictPtrPtrStore, out LLVMValueRef fatFunctionPtr);
builder.BuildCall(fn, new LLVMValueRef[] {throwingFunction.GetParam(0) }, string.Empty);
builder.BuildUnreachable();
return fn;
}

private LLVMValueRef GetInstanceFieldAddress(StackEntry objectEntry, FieldDesc field)
Expand Down
2 changes: 2 additions & 0 deletions src/ILCompiler.WebAssembly/src/CodeGen/ILToWebAssemblyImporter_Statics.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -129,6 +129,8 @@ public static void CompileMethod(WebAssemblyCodegenCompilation compilation, WebA
static LLVMValueRef SubOvfUn32Function = default(LLVMValueRef);
static LLVMValueRef SubOvf64Function = default(LLVMValueRef);
static LLVMValueRef SubOvfUn64Function = default(LLVMValueRef);
static LLVMValueRef Abs32Function = default(LLVMValueRef);
static LLVMValueRef Abs64Function = default(LLVMValueRef);
public static LLVMValueRef GxxPersonality = default(LLVMValueRef);
public static LLVMTypeRef GxxPersonalityType = default(LLVMTypeRef);

Expand Down
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